| Abstract: Thus, this work aims at verifying both microbial and cytoxic effects of aqueous and saline extracts of Moringa oleifera seeds utilized as natural coagulants in water treatment. Microbial activity was verified by means of microdilution technique in plates in order to determine MIC (Minimum Inhibitory Concentration) and microculture in agar for the determination of MBC (Minimum Bacterial Concentration). One possible action mechanism of the extracts was assessed by means of flow Cytometry followed by scanning electron microscopy and the cytotoxicity was carried out by MTT method, using Vero cells. The possibility of action of the extract on cell membrane of micro-organisms was significant, since the flow cytometry presented values of about 50% alteration. This alteration was confirmed by scanning electron microscopy and may constitute a hypothetical action mechanism of the extract. The saline extract at 1.9 mg/mL concentration reduced cell viability to 50%, showing lower cytotoxicity towards VERO cells in comparison with the aqueous extract, which presented low viability at 0.2 mg/mL, whose CC50 lies below this value. The micro-organisms that presented more sensitivity to the aqueous extract were Staphylococcus aureus, Aeromonas hydrofila and Escherichia coli, with MIC values of 1.56, 3.12 and 30 mg/mL and MBC values of 30, 6.25 and 40 mg/mL, respectively. The same micro-organisms also presented lower values of MIC and MBC for the saline extract. Both extracts presented similar MIC values (90 mg/mL) for Klebsiella pneumoniae and Pseudomonas aeruginosa. The results indicate activity against the tested micro-organisms, but with some toxicity relative to VERO cells, pointing to the necessity of a thorough study of cytoxicity of this extract for the use in water treatment. It is proposed that further studies, using extracts combined with physical and chemical methods of treatment, be carried out to potentiate the antimicrobial effect of Moringa oleifera seeds and reduce its toxicity. |
